Chemical heat pump comprising an active surface

ABSTRACT

Chemical heat pump comprising an active surface. A chemical heat pump working according to the hybrid principle with an active substance and a volatile liquid whereby the active substance is in a reactor part  1  and the volatile liquid is in a condenser/evaporator part  3 , while the volatile liquid is moving between these parts  1, 3  to be absorbed and desorbed by the active substance and be condensed and evaporated in the condenser/ evaporator part. The reactor part may comprise a layer  12  for the active substance so that this at least in its liquid phase is retained in the layer and the condenser/evaporator part may comprise a layer  13  for the volatile liquid so that this in its liquid phase is retained in the layer. Advantages of a falling film process are combined with the advantages of a matrix material in a chemical heat pump.

TECHNICAL FIELD

The present invention relates generally to a chemical heat pump withextended functionality. More in particular it relates to a chemical heatpump working according to the hybrid principle and wherein there is anactive surface in the chemical heat pump.

BACKGROUND

In prior art chemical heat pumps working according to the hybridprinciple are already known. In chemical heat pumps working according tothe hybrid principle the active substance is in both solid and liquidphase during the process. These two phases are utilized to give animproved storage of energy. A volatile liquid such as water is absorbedby and then desorbed from the active substance. The liquid phase of theactive substance is during charging spread out over a heat conductingmaterial such as a heat exchange surface for exchange of heat in thereactor part of the chemical heat pump. The liquid phase is heatedduring charging and the liquid is desorbed fmm the active substance andmoved in gas phase to a condenser/evaporator part of the chemical heatpump. In the condenser/evaporator the gas in condensed to liquid andcollected. During discharge of the chemical heat pump the liquid isevaporated in the condenser/evaporator and moved to the reactor part,whereby the gas condenses to liquid and is absorbed by the activesubstance.

In earlier known chemical heat pumps working according to the hybridprinciple the falling film process is for instance utilized. The liquidphase of the active substance and the liquid is sprayed by pumps over aheat conducting material at an upper level of the reactor and thecondenser/evaporator part respectively, for exchange of heat duringcharging and discharging of the chemical heat pump. A thin film ofliquid comprising the active substance in liquid phase in the reactorpart and liquid in the condenser/evaporator part is spread out over theheat conducting material for exchange of heat and is falling downthrough the reactor part or condenser/evaporator part because of thegravity. The liquid phase and the liquid eventually reach the bottomlevel of the reactor part and the condenser/evaporator partrespectively, whereby pumps again pump the liquid to the upper level ofthe chemical heat pump whereby the falling film process continues. Anadvantage of a falling film process is that the heat conductive materialis completly exposed to the liquid phase and the liquid respectively,because the liquid film on the heat conducting material is thin.Condensation of gas and evaporation of liquid can thereby be efficient.

A problem with the falling film process is that particles of activesubstance in solid phase may form, and they may obstruct for instance inthe pumps. In order to avoid this problem the formation of activesubstance in solid phase is normally avoided when using the falling filmprocess.

A solution to the above described problem with the falling film processis disclosed in the Swedish patent SE 515 688, where a net is used tohold the active substance in its solid phase so that particles of solidactive substance in the pumps can be avoided. When the formation ofsolid active substance can be allowed, it is possible to store moreenergy.

A development of the chemical heat pump according to the Swedish patentSE 515 688 is disclosed in the Swedish patent SE 530 959. In this laterpatent there is disclosed a chemical heat pump which utilizes the samebasic principle but where the net is exchanged with a layer in the formof a matrix. The matrix holds the active substance both in its liquidand solid phase and is distributed as a layer over the heat conductivematerial. The matrix is inert and permeable to the liquid phase. Anadvantage with such a chemical heat pump is that a large amount ofactive substance in solid or liquid phase can be bound to the matrix sothat the chemical heat pump can contain a large amount of energy. Thematrix has the property that it is able to absorb the liquid and theliquid phase of the active substance. With the matrix no pumps arerequired as in earlier falling film processes.

In certain cases there is a mom for improvement regarding chemical heatpumps with a matrix. The matrix is in contact with the heat conductivematerial so that the heat conductive material is covered by the matrix.Evaporation of the volatile liquid and condensing of the gas phase maythereby take somewhat longer time compared to a case where the heatconductive material is directly exposed to the volatile liquid and thegas phase. The transport of gas to and fmm the heat conductive materialand between the reactor part and the condenser/evaporator part may besomewhat impaired. Further the matrix causes a pressure drop when gaspasses the matrix.

In the prior art there is thus a need for an improved chemical heat pumpworking according to the hybrid principle.

SUMMARY

It is an object of the present invention to obviate at least some of thedisadvantages in the prior art and provide an improved chemical heatpump.

In a first aspect there is provided a chemical heat pump comprising anactive substance and a volatile liquid, said volatile liquid beingadapted to be absorbed by the active substance at a first temperatureand said volatile liquid being adapted to be desorbed by the activesubstance at a second higher temperature, whereby the active substanceat the first temperature has a solid phase, fmm which the activesubstance during uptake of the volatile liquid and its gas phaseimmediately transforms partially into liquid phase or liquid phase andwhereby the active substance at the second higher temperature has aliquid phase or is in liquid phase, from which the active substanceduring desorbtion of the volatile liquid, in particular the gas phase ofthe volatile liquid, immediately transforms partially into solid phase,whereby the chemical heat pump comprises:

a reactor part 1 comprising active substance, whereby the reactor part 1is adapted to exchange heat with an external medium 4 by exchange ofheat through deliniting and heat conducting walls 9,11,

a condenser/evaporator part 3 comprising a part of the volatile liquid,the condenser/evaporator part 3 being adapted to exchange heat with anexternal medium 6 by exchange of heat through delimiting and heatconducting walls 9,11, and

a passage 2 for the gas phase of the volatile liquid, said passageconnecting the reactor part 1 and the condenser/evaporator part 3 witheach other,

whereby at least one of i the reactor part 1 and ii thecondenser/evaporator part 3 comprises a layer 12, 13, 16,

whereby a layer 12, 16 if present in the reactor part 1 is adapted toretain the active substance at least in its liquid phase or its liquidphase, and whereby a layer 13, 16 if present in the condenser/evaporatorpart 3 is adapted to retain the volatile liquid in its liquid phase,

wherein

the layer 12, 13, 16 is arranged as bodies with limited contact surfacesagainst the surface of one or more of the heat conducting walls 9, 11 sothat free areas 14, 15 of the surfaces of the heat conducting walls 9,11 are between the contact surfaces,

that the free areas 14, 15 of the surface of the heat conducting walls9, 11 are adapted to exert a net attractive force on the activesubstance in its liquid phase and the volatile liquid in its liquidphase respectively and that the net attractive force is adjusted withregard to net attractive force exerted by the layer 12, 13, 16 on theactive substance in its liquid phase and the volatile liquid in itsliquid phase respectively.

In one embodiment the layer 12, 13, 16 comprises a matrix and whereinthe matrix comprises a porous material which is permeable to the gasphase of the volatile liquid.

In one embodiment said net attractive force exerted by the free areas14, 15 of the surface of the heat conducting walls 9, 11 comprisescapillary force.

In one embodiment the layer 12, 13, 16 comprises a material which hasadjusted capillary properties with regard to the active substance in itsliquid phase and the volatile liquid in its liquid phase respectively.

In one embodiment the layer 12, 13, 16 comprises surfaces which haveadjusted wetting properties with regard to the active substance in itsliquid phase and the volatile liquid in its liquid phase respectively.

In one embodiment the net attractive force exerted by the free areas 14,15 of the surface of the heat conducting walls 9, 11 is adjusted so thatthe net attractive force exerted by the heat conducting walls 9, 11 onthe active substance in its liquid phase and the volatile liquid in itsliquid phase respectively, is higher than the net attractive forceexerted by the layer 12, 13, 16 on the active substance in its liquidphase and the volatile liquid in its liquid phase respectively.

In one embodiment the limited contact surfaces constitute maximum 10%,preferably maximum 5% of the area of the heat conducting walls 9, 11.

In one embodiment the bodies of matrix are designed as parallel discswith a through hole and the outer surfaces of the discs are in contactwith the surface of a heat conducting wall.

In one embodiment the bodies of matrix are arranged as bodies whichextend between opposite walls in parallel channels 22 in a plate heatexchanger, whereby other parallel channels 23 in the plate heatexchanger comprises a heat carrying medium.

The advantages of an exposed surface of a heat conducting material in afalling film process are combined with the advantages of a matrix forstorage of active substance in solid and liquid phase.

One advantage is that the transport of gas to and from the heatconductive material is improved. The pressure drop caused when gaspasses the matrix is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to theaccompanying drawings, in which

FIG. 1 a is a schematic drawing of a known chemical heat pump workingaccording to the hybrid principle with a matrix according to the stateof the art,

FIG. 1 b is a schematic drawing similar to FIG. 1 a, in which the matrixis arranged in a different way compared to the relation between innersurfaces in the reactor part and condenser/evaporator part in thechemical heat pump,

FIG. 2 shows how the liquid phase of an active substance in a reactor orvolatile liquid in a condenser/evaporator in a chemical heat pump istransported from an active surface to a layer and,

FIG. 3 is a sectional view of a heat exchanger with parallel channels,of which some channels are reactor or condenser/evaporator in a chemicalheat pump and other channels are for circulation of an outer heatcarrying medium.

DETAILED DESCRIPTION

Before the invention is disclosed and described in detail, it is to beunderstood that this invention is not limited to particular compounds,configurations, method steps, substrates, and materials disclosed hereinas such compounds, configurations, method steps, substrates, andmaterials may vary somewhat It is also to be understood that theterminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting since thescope of the present invention is limited only by the appended claimsand equivalents thereof.

It must be noted that as used in this specification and the appendedclaims, the singular forms “a”, “an” and “the” include plural referentsunless the context clearly dictates otherwise.

If nothing else is defined, any terms and scientific terminology usedherein are intended to have the meanings commonly understood by those ofskill in the art to which this invention pertains.

The term “about” as used in connection with a numerical value throughoutthe description and the claims denotes an interval of accuracy, familiarand acceptable to a person skilled in the art. Said interval is ±10%.

In a chemical heat pump working according to the hybrid principle theremay be in one of or both of the reactor part and thecondenser/evaporator part be collecting areas, denoted layers, whichattract the active substance in its dissolved liquid phase and thevolatile liquid respectively so that the layer can take up more or lessof the active substance in its dissolved liquid phase and more or lessof the volatile liquid in its liquid phase. The attraction isaccomplished in a suitable way such as with the aid of a capillary forceand/or wetting forces. These layers are arranged as delimited bodieswith only such a limited contact with the outer wall in a reactor partand condenser/evaporator part respectively so that there between thecontact surfaces are free areas of the inside of the outer wall. Thesefree areas also have a capillary and/or wetting ability, which in asuitable way is adapted to the attractive capillary and wetting abilityof the layers and constitute areas which may have heat exchange with anexternal medium across only the wall, which may be thin, and on thesurface of which the free areas are situated. Such a nearly direct heatexchange is efficient and is relatively quick

The layers may be shaped as bodies of matrix material designed accordingto the above mentioned Swedish patent SE 530 959. In another case thelayers comprise other suitable bodies with capillary suction and/orwetting inner surfaces, for instance two discs of ceramic material suchas glass disks, which opposing surfaces are capillary and/or wetting forthe active substance in its liquid phase and the volatile liquid andbetween which liquid can be sucked in.

With such a chemical heat pump comprising an exposed surface of a heatconducting wall combined with a layer for storage of for instance activesubstance in its liquid phase it is possible to achieve the same effectper surface area as for the falling film process without usingmechanical pumps, such as electrical pumps. When using matrix materialin the storage bodies it is possible to retain the large storagecapacity of the matrix.

With the chemical heat pump a higher power per unit area may be reached.This can for instance be utilized so that a smaller amount of materialmay be used for manufacture of the chemical heat pump and so that itsize thereby can be reduced. This may lead to lower manufacturing costsfor the chemical heat pump. A chemical heat pump in which a higher poweris reached per unit area may also open new possibilities forapplications. Such a heat pump could for instance be used for fastprocesses, during which charging and discharging can be performed duringminutes instead of hours as the heat pumps according to the prior art.In order to achieve this it is important that the surface of the heatconducting material is as well exposed as possible and at leastpartially not covered by a matrix.

The chemical heat pump thus has free exposed active surface areas ofheat conducting walls and a layer for a liquid phase, whereby both theactive surface and the layer have an ability to attract the liquid phasefor instance by capillary action and/or wetting. The drawbacks of amatrix can thereby be eliminated and the advantage of a large storagecan be maintained.

The disclosed heat pump is thus in general of the type with an activesubstance and a volatile liquid, whereby the liquid may be absorbed bythe substance at a first temperature and desorbed by the substance at asecond higher temperature. The active substance has at the firsttemperature a solid phase, from which it during uptake of the volatileliquid and its gas phase immediately transforms partially to a liquidphase or liquid phase. At the second temperature it has a liquid phaseor is in liquid phase, from which it during desorbtion of the volatileliquid, in particular its gas phase, immediately transforms partiallyinto solid phase. The chemical heat pump in general comprises thefollowing parts:

-   -   A reactor part comprising the active substance and which is        adapted to exchange heat, i.e. to be heated and/or cooled by an        external medium by exchange of heat through one or more        delimiting heat conducting walls.    -   A condenser/evaporator part comprising essentially the part of        the volatile liquid which is in condensed form and which is        designed to exchange heat, i.e. to be heated and cooled by an        external medium by exchange of heat through one or more        delimiting heat conducting walls.    -   A passage for the gas phase of the volatile liquid, which        passage connects the reactor part and the condenser/evaporator        part with each other.

The reactor part can comprise a layer intended for the active substance,which in one embodiment may comprise a matrix in the form of a porousmaterial, so that the active substance at least in its liquid phase orin its liquid phase can be retained in and/or be bound to the matrix.Alternatively or in combination the condenser/evaporator part maycomprise a layer for the volatile liquid, which may comprise a matrix inthe form of a porous material, which material is permeable for the gasphase of the volatile liquid, so that the volatile liquid in its liquidphase can be retained in and/or be bound to the matrix.

The matrix can in one part or in both parts be arranged as bodies, whichmay be designed as discs or plates and have limited contact surfacesagainst the inner surface of the one or more heat conducting walls. Inone embodiment the layer 12, 13, 16 is arranged as discs. In oneembodiment the layer 12, 13, 16 is arranged as plates. In one embodimentthe layer 12, 13, 16 is arranged as discs and plates. Free areas of thesurfaces of the heat conducting walls then exist between the contactsurfaces. These free surfaces of the heat conducting walls may havecapillary properties and/or wetting properties for the active substancein its liquid phase and for the volatile liquid in its liquid phaserespectively. In particular so that the free areas of the surfaces ofthe heat conducting walls have capillary properties or wettingproperties for the active substance in its liquid phase and for thevolatile liquid in its liquid phase respectively, which is larger thanthe capillary properties of the matrix with regard to the activesubstance in its liquid phase and the volatile liquid in its liquidphase respectively, i.e. so that the active substance in its liquidphase and the volatile liquid in its liquid phase is easier attracted,sucked into, and/or distributed and spread over the free areas of thesurfaces of the heat conducting walls compared to the matrix.

The limited contact surfaces have in general a minimum or relative smallarea, so that they constitute a relatively small part of the surface ofa heat conducting wall. They may for a heat conducting wall togetherconstitute maximum 10%, or maximum 5% of the surface of the heatconducting wall.

In the chemical heat pump depicted schematically in FIG. 1 a there aretwo compartment. A first compartment constitutes the reactor part 1,comprising an active substance, which in an exothermic reaction canabsorb and in an endothermic reaction can desorb the vapor or gas phaseof a volatile liquid. The reactor part 1 is via a tube or channel 2connected to a second compartment, which constitutes acondenser/evaporator part 3. The second compartment 3 acts as acondenser for condensing the gas phase of the volatile liquid to itsliquid phase and as en evaporator of the volatile liquid in its liquidphase to gas. The active substance in the reactor part 1 is in heatexchanging contact with an external heat carrying medium 4, which isshown by the arrows 5 for addition or removal of heat The liquid in thecondenser/evaporator part 3 is also in heat exchanging contact with asecond external heat carrying medium 6, which is shown by the arrows 7,for addition or removal of heat

According to the hybrid principle the active substance changes betweensolid phase and solution state. For the chemical heat pump to workaccording to the hybrid principle, the active substance has to remain inthe reactor part 1. One way of accomplishing this is by using a net tolimit the movements of the active substance in its solid phase. Anotherway is to use a matrix 8 which also may function as energy storage. Sucha matrix holds the active substance both in it liquid and solid phaseand is inert with respect to the used active substance and the volatileliquid in their different phases. Further the matrix is permeable forthe volatile liquid in its gas phase and may be arranged inside thereactor part 1 in the form of a layer 8 on an inner surface of one orseveral walls 9. The inner surface of the walls 9 are in contact withthe first outer heat carrying medium 4. On the inner surfaces of walls11 in the condenser/evaporator part 3 similar layers of matrix 10 may bearranged, which matrix is used to retain and bind the volatile liquid inits liquid phase.

In such a chemical heat pump a relatively large amount of activesubstance can be retained in the matrix 8. The chemical heat pump canthen contain a large energy storage. The matrix is of a material, whichhas the property the surface of the material can be wetted by volatileliquid, and thereby that it can bind to the volatile liquid in it liquidphase. The same is true for the liquid phase of the active substance.

In the prior art and as depicted in FIG. 1 a the matrix 8, 10 is incontact with the heat conducting material in the walls 9, 11. The innersurface of the walls is thereby not directly exposed to the gas phase ofthe volatile liquid and the gas phase is thereby not in direct heatconducting contact with the wall material and can thus for instance notbe cooled with maximum efficiency and not quickly. Similarly the activesubstance in its liquid phase or liquid phase is not in direct heatexchanging contact with the wall material, which does not give acorrrpletely efficient or at least not a quick heat transfer, forinstance for evaporation of the liquid in the active substance in itsactive form. The corresponding is true for the condenser/evaporatorpart. The slow heat exchange can be said to correspond to a pressuredrop accomplished by the matrix when vapor or gas is passing the matrix.

In order to achieve direct contact between the gas phase and the innersurfaces of the heat conducting walls 9, 11, large areas of those wallsare left free from matrix whereas the matrix is arranged as a collectionarea or storage designed as one or more bodies 12, 13, which only haverelatively limited contact area against the inner surfaces of the walls,see FIG. 1 b. It is desirable that the gas phase of the volatile liquidis able to pass these bodies and these can be made as relatively thinlayers. Such layers of matrix can for instance and as indicated in FIG.1 b be arranged as essentially parallel relatively thin discs with oneor several holes such as a centered through hole to allow passage of gasbetween the different part of the compartment 1, 3.

liquid which has condensed or has formed in the surface of the freeareas 14, 15 of the heat exchanging walls 9, 11, shall be able to beretained in the storages, i.e. in the bodies 12, 13. This may beaccomplished if the material in the bodies have a sucking or attractiveforce, for instance a capillary action on the liquid phase of the activesubstance and the volatile liquid respectively, which is adjusted to orin relation to the adhesion or wetting, which the liquid phase of theactive substance and the volatile liquid respectively has to the surfaceof the free areas 14, 15 of the inside of the walls. The adhesion orwetting which the liquid phase of the active substance and the volatileliquid respectively to the surface of the free areas of the inside ofthe walls, is suitably adapted in relation to the adhesion of thematerial in the bodies for the liquid phase of the active substance andthe volatile liquid respectively.

When there is plenty of liquid phase of the active substance andvolatile liquid respectively in the free areas 14, 15 the liquid isaffected by the attractive forces and sucked into the storages, i.e. thematrix in the bodies 12, 13 and is temporarily retained there. On thecontrary when there is plenty of liquid phase of the active substanceand volatile liquid respectively in the bodies 12, 13, the liquid phaseof the active substance and volatile liquid respectively is spread outas a layer on the surface of the free areas 14, 15, where it easily andquickly can be evaporated by the almost direct heat transfer, which isaccomplished by heat transfer through the walls 9, 11.

The mentioned adhesion or wetting, i.e. attraction, which the activesubstance and volatile liquid respectively has for the surface orsurface layer in the free areas 14, 15 of the heat conducting walls, andwhich cause the active substance and volatile liquid respectively tospread out over these areas can be accomplished if desired by a surfacetreatment in order to achieve the desired properties. This can forinstance be accomplished by coating the surface of the heat conductingmaterial in the walls 9, 11, with a suitable capillary material or witha material with suitable wetting properties. The surface of the heatconducting wall may be treated mechanical, chemical or electrical.

When the surface of the free areas is coated with a capillary materialthe mentioned adhesion or wetting which the active substance andvolatile liquid respectively has for the surface of the free areas 14,15 of the heat conducting walls 9, 11, is equivalent with that thesurface has a capillary action for the active substance and volatileliquid respectively. Such layers with capillary material may have athickness in the range 10 μm-1 mm.

If the wetting or adhesive ability or the capillary properties of theactive surface is adapted in a suitable way, it can to a large extentcontribute to that the liquid phase can efficiently be spread out overthe free areas 14, 15 of the heat conducting wall material in the outerwalls 9, 11 for exchange of heat during charge and dischargerespectively. The chemical heat pump can then be operated with highpower.

The active surface can for instance comprise the capillary materialAl₂,O₃. The capillary material can be bound together with SiO₂ but thereare also other alternatives for adhesion of the capillary material tothe heat conducting wall material. The active surface is preferablyinert, i.e. the surface should not participate chemically in thechemical heat pump process. According to the teachings above theproperties of the active surface are adapted so that the active surfaceobtains an ability to give the desired capillary or wetting attractiveforces on the active substance and volatile liquid respectively, whichare used in the chemical heat pump.

The storages i.e., the bodies 12, 13 shall in general have properties sothat they can attract and retain a certain amount of the activesubstance and volatile liquid respectively. It is then not entirelynecessary that they are permeable to the gas phase of the volatileliquid. The storages can thus be designed as surface with suitablyadapted wetting properties and/or be designed with capillaries, i.e.with capillary channels. Thus the material in a matrix may for instance,if such a matrix is used, comprise pores or capillaries with so smalldiameter that they act with capillary force on the respectively fluid.

In a chemical heat pump according to above no pump is utilized to spreadout the liquid phase of the active substance and the volatile liquidrespectively over the surface of the heat conducting wall materialduring charge and discharge. The liquid phase of the active substanceand the volatile liquid respectively is instead spread out over thesurface of the heat conducting wall material through the capillaryforces in the active surface. Thereby the chemical heat pump can beconstructed with fewer number of parts and without mechanical pumps,often electrical driven pumps, which otherwise would decrease the totalenergy recovery due to their power consumption. In the chemical heatpump described herein the heat energy is utilized to accomplish theequivalent work, which in this chemical heat pump is attraction onmolecular level, capillary and/or wetting.

In FIG. 2 there is shown the principles how the liquid phase of activesubstance in the reactor part 1 or volatile liquid in thecondenser/evaporator part 3 is pumped from a storage 16 such as a matrixout and over an active surface 17 or alternatively how the liquid phaseof active substance in the reactor part 1 or volatile liquid in thecondenser/evaporator part 3 is pumped from the active surface 17 to thestorage 16.

In contrast to the matrix described in the above mentioned Swedishpatent 530 959, the matrix 12, 13 in the present chemical heat pump isarranged so that it only marginally affects evaporation en condensation,i.e. the matrix is arranged so that it only is in contact with a minimumof the surface of the heat conducting wall material, through whichexchange of heat occurs, see FIG. 1 b and FIG. 2. In some exceptionalcases the energy storage 16 is not at all in contact with the surface17. In contrast to the construction disclosed in the Swedish patent 530959, essentially the entire surface, or at least 90% or at least 95% ofthe heat conducting material in the walls 9, 11 is directly accessiblefor evaporation/condensing, whereby this is accomplished without oressentially without or with only little pressure drop for the gas phase,moving between the different park of the chemical heat pump. Sinceessentially or almost the entire inner surface of the heat conductingwalls can be held free of matrix, an efficient gas transport and therebya high output can be achieved. The amount of gas which can betransported to and from the heat conducting wall material in the walls9, 10 is larger than in the known construction.

The storage 12, 13 for the liquid phase is arranged so that the liquideither by suitable forces such as capillary and/or wetting forces ispumped out of the storage or in the other process phase of the chemicalheat pump by suitable forces such as capillary and/or wetting forces ispumped back to the storage. The storage is constructed so that it by aidof suitable forces is able to retain the active substance in its liquidphase in the reactor part 1 and in the condenser/evaporator part 3retain the volatile liquid. The forces acting on the liquid phase or thevolatile liquid in the storage 12, 13 is in one embodiment adjusted sothat these net attractive forces are not as strong as the net attractiveforces of the active surface in the free areas 14, 15, which act in asimilar way on liquid phase of volatile liquid. The liquid phase or thevolatile liquid can thereby be fed out from the storage 12, 13 on to theactive surface in the free areas of the inner side of the outer walls 9,11. For instance during charging of the chemical heat pump the liquidphase in the reactor part 1 is fed out onto the active surface asdescribed below.

An example of an empiric formula for calculation of the capillary forcein the active surface, if it is designed as a layer comprising particlesis:

$W_{a.s.} = {k\; \sigma^{2}\; \frac{\cos^{2}{\theta \left( {\frac{1}{d_{{as}\;}} - \frac{1}{d_{s}}} \right)}}{\rho \; g\; \mu \; L}}$

Wherein W_(a.s) is capillary average pump speed in the active surfacefor penetration length L, i.e. the length which the liquid phase travelsin the capillary system.

K is a constant

σ is the surface tension of the liquid,

θ is the contact angle of a drop of the liquid against the activesurface

ρ is the density of the liquid,

g is the gravity constant,

μ is the viscosity of the liquid,

L is the penetration length

d_(a.s.) is the particle diameter in the capillary layer of the activesurface, and

d_(s) is the particle diameter in the energy storage.

This formula is based on tests with an active surface and a layer 12, 13comprising particles with different particles sizes. The formula isvalid for penetration lengths L of about 5-40 mm. As seen from theformula the pump speed in the active surface has a meaningful value onlywhen the condition 1/d_(as)>1/d_(s) is fulfilled. The experimentalmeasurements have shown that the optimum relation between d_(as) andd_(s) in on embodiment is about 1:3.

When the chemical heat pump is charged the reactor part 1 can be heatedto a suitable temperature with a heat source, for instance the sun,which heats the first outer medium 4, or directly the outer surface ofthe heat conducting walls 9. During charging it is generally arranged sothat the reactor part 1 because of external influence gets a highertemperature than the condenser/evaporator part. The active substance isduring the initial part of the charge in liquid phase and retained inliquid phase in the storage 12 in the reactor part 1.

Because the material in the storage 12 and the active surface 14 areadjusted so that the capillary forces in the layer are not as strong asthe capillary forces or the wetting forces in the heat conductingmaterial of the active surface, the liquid phase can gradually be fedout and spread out over the active surface i.e. the inner free surfaceof the heat conducting wall material. Due to the properties of theactive surface of the heat conductive material, the active substance init liquid phase is fed out to and distributed over the surface of theheat conducting wall material. Finally the capillary system is saturatedin the active surface by the liquid phase of the active substance,whereby further liquid in the liquid phase of the active substance canbe evaporated fmm the active surface and travel to thecondenser/evaporator part 3. Hereby more or less solid, active substanceis formed on and in the active surface. When the liquid is evaporatedfmm the active substance, new liquid liquid phase can by capillaryforces be pumped out from the storage to the active surface and out overthe heat conducting wall material. A continuous feed of liquid phase tothe surface of the heat conducting wall material thus occurs.

In the condenser/evaporator part 3 the evaporated liquid is simultaneouscondensed, when it comes into contact with the surface of the free areas15 of the heat conducting wall material of the walls 11, which here arecooled by the second external medium 6. The liquid is pumped capillaryinto the matrix 13 and more steam can thereby continuously be condensedand the process can continue. The condensed liquid can be pumped intothe matrix even if the capillary forces are not as strong as thecapillary forces or the wetting forces of the active surface, becausethe capillary system in the active surface becomes saturated and cannotretain more liquid, whereby the liquid flows on the active surface andcan be sucked into the capillary system of the matrix.

In the beginning of the discharge of the present chemical heat pump theactive substance is most often mainly in its solid phase on the activesurface 14 in the reactor part 1 and the liquid is retained in thematrix 13 in the condenser/evaporator part 3. The external heatingand/or external cooling of the reactor part and the condenser/evaporatorpart ceases and can if required or if it is suitable with regard to theapplication area be replaced by external cooling and/or with externalheating respectively. Liquid is pumped out from the matrix 13 bycapillary forces in the condenser/evaporator part and out over the freeareas 15 of the surfaces of the heat conducting material because thesesurfaces have a surface which is active according to the descriptionabove. The liquid on the active surface is evaporated and partiallytransferred to the reactor part 1. This process occurs continuouslybecause new liquid is pumped out on the surface of the heat conductingmaterial when the liquid is evaporated. When the gas phase of the liquidreaches the reactor part 1 it is condensed and when it comes intocontact with the inner surface of the heat conducting walls 9. Theactive substance on the inner surface 14 absorbs the liquid andtransforms into its liquid phase, whereby the liquid phase by capillaryforces is distributed over the surface of the inner side of the heatconducting walls and finally are pumped into the storage 12 by capillaryforces, as soon as there is a surplus of the liquid phase so that thecapillary forces in the storage can act on the liquid. More gas from thecondenser/evaporator part 3 can thereby continuously be condensed andabsorbed by the active substance.

In one embodiment the reactor part and/or the condenser/evaporator partis arranged in a conventional plate heat exchanger. In one embodiment ina heat exchanger of cross flow type, see FIG. 3. In such a plate heatexchanger there are corrugated heat conducting walls 21, which arearranged next to each other with different surface in close contact witheach other. Between the heat conducting walls 21 there are firstparallel channels 22, in which the external medium 4, 6 may be and betransported. Between the heat conducting walls 21 there are also secondparallel channels 23. These second channels 23, which as shown may bearranged essentially perpendicular to the first channels, are spaces forthe reactor and condenser/evaporator respectively in a chemical heatpump. In each such second channel 23, which constitutes a space for thereactor or condenser/evaporator in a chemical heat pump as describedabove a stripe or disc 24 of matrix material may be arranged. The stripeor disc is placed so that it extends between opposing walls in thechannel, for example centered in the channel.

The second channels 23 in a heat exchanger unit of the type shown inFIG. 3, can in a suitable way be connected to the second channels in asimilar heat exchanger so that the second channels in the first heatexchanger form spaces for the reactor part in a chemical heat pump andthe second channels in the second heat exchanger form space for thecondenser/evaporator part.

The first channels 22 can for instance be more or less designed asordinary conduits while the second channels 23 as shown can have alens-shaped cross section. Of the walls 21 are essentially horizontal,then the cross section of the second channels have a downwards bendbottom and an upwards bent upper part The stripe or disc 24 of matrixmaterial can as shown extend between the bent bottom surface and thebend upper part of the channel.

The heat conducting walls of both the reactor part 1 and thecondenser/evaporator part may thus be bent Such a bent shape at thebottom part of the second channels 23 may facilitate the transport ofliquid over the surface of the walls 21, so that when a surplus ofliquid exists, it will gather in the bottom of the channel and beabsorbed by the matrix material 24.

Application areas for a chemical heat pump comprising an active surfaceand a layer as described above include but are not limited to allprocesses where heat energy is available continuously. In particular thechemical heat pump can be used in cases where energy does not have to bestored during extended periods, but where a lot of power has to beutilized and delivered respectively. Examples of such uses include butare not limited to more efficient use of an ordinary oil, wood, or gasheater. In one embodiment the heater can continuously deliver heat tothe chemical heat pump and it is only desired to store energy for about20-30 minutes. If the described chemical heat pump is used together withan existing heater, twice as much energy can be recovered from theheater in one embodiment, whereby about ¾ is heat and about ¼ is coolingin one embodiment

Another example is air condition for vehicles, where continuous excessheat from the internal combustion engine can be transformed intocooling. This may in one embodiment reduce the fuel consumption with5-25% for buses. Another example where electricity is generated from aninternal combustion engine, because the excess heat which is cooled awayin one embodiment constitutes about 70% of the fuel consumption. Byusing the described technology with the chemical heat pump comprising anactive surface and storage more than half of this energy can beconverted into heat or cooling, in one embodiment

Other features and uses of the invention and their associated advantageswill be evident to a person skilled in the art upon reading thedescription and the examples.

It is to be understood that this invention is not limited to theparticular embodiments shown here. The following examples are providedfor illustrative purposes and are not intended to limit the scope of theinvention since the scope of the present invention is limited only bythe appended claims and equivalents thereof.

1. A chemical heat pump comprising an active substance and a volatileliquid, said volatile liquid being adapted to be absorbed by the activesubstance at a first temperature and said volatile liquid being adaptedto be desorbed by the active substance at a second higher temperature,whereby the active substance at the first temperature has a solid phase,from which the active substance during uptake of the volatile liquid andits gas phase immediately transforms partially into liquid phase orliquid phase and whereby the active substance at the second highertemperature has a liquid phase or is in liquid phase, from which theactive substance during desorbtion of the volatile liquid, in particularthe gas phase of the volatile liquid, in particular the gas phase of thevolatile liquid, immediately transforms partially into solid phase,whereby the chemical heat pump comprises: a reactor part comprisingactive substance, whereby the reactor part is adapted to exchange heatwith an external medium by exchange of heat through delimiting and heatconducting walls, a condenser/evaporator part comprising a part of thevolatile liquid, the condenser/evaporator part being adapted to exchangeheat with an external medium by exchange of heat through delimiting andheat conducting walls, and a passage for the gas phase of the volatileliquid, said passage connecting the reactor part and thecondenser/evaporator part with each other, whereby at least one of (i)the reactor part and (ii) the condenser/evaporator part comprises alayer, whereby a layer if present in the reactor part is adapted toretain the active substance at least in its liquid phase or its liquidphase, and whereby a layer if present in the condenser/evaporator partis adapted to retain the volatile liquid in its liquid phase, that thelayer is arranged as bodies with limited contact surfaces against thesurface of one or more of the heat conducting walls so that free areasof the surfaces of the heat conducting walls are between the contactsurfaces, that the free areas of the surface of the heat conductingwalls are adapted to exert a net attractive force on the activesubstance in its liquid phase and the volatile liquid in its liquidphase respectively and that the net attractive force is adjusted withregard to net attractive force exerted by the layer on the activesubstance in its liquid phase and the volatile liquid in its liquidphase respectively.
 2. The chemical heat pump according to claim 1,wherein the layer comprises a matrix and wherein the matrix comprises aporous material which is permeable to the gas phase of the volatileliquid.
 3. The chemical heat pump according to claim 1, wherein said netattractive force exerted by the free areas of the surface of the heatconducting walls comprises capillary force.
 4. The chemical heat pumpaccording to claim 1, wherein the layer comprises a material which hasadjusted capillary properties with regard to the active substance in itsliquid phase and the volatile liquid in its liquid phase respectively.5. The chemical heat pump according to claim 1 wherein the layercomprises surfaces which have adjusted wetting properties with regard tothe active substance in its liquid phase and the volatile liquid in itsliquid phase respectively.
 6. The chemical heat pump according to claim1, wherein the net attractive force exerted by the free areas of thesurface of the heat conducting walls is adjusted so that the netattractive force exerted by the heat conducting walls on the activesubstance in its liquid phase and the volatile liquid in its liquidphase respectively, is higher than the net attractive force exerted bythe layer on the active substance in its liquid phase and the volatileliquid in its liquid phase respectively.
 7. The chemical heat pumpaccording to claim 1, wherein the limited contact surfaces constitutemaximum 10%, preferably maximum 5% of the area of the heat conductingwalls
 0414. 8. The chemical heat pump according to claim 1, wherein thebodies of matrix are designed as parallel discs with a through hole andthe outer surfaces of the discs are in contact with the surface of aheat conducting wall.
 9. The chemical heat pump according to claim 1,wherein the bodies of matrix are arranged as b_(o)dies which extendbetween opposite walls in parallel channels in a plate heat exchanger,whereby other parallel channels in the plate heat exchanger comprises aheat carrying medium.